1.someone who has had it, needs to stick a fork in it, has hit rock bottom, needs to go home and get some sleep, put the pipe down and find a hole and crawl in it.
2.someone who is not in their right mind and acts like it. acts with no regard, especially in public.
3.a person that looks like sh*t because of their own lack of self respect
4.also the name of an underground clothing label from los angeles

"look at her, she is coming down all over the place,her hair looks like shit,smells like yesterday, head all swollen, somebody take that DUSTMONKEY home and don't give her anymore shit!"